Yes I kept piwik up to date, in the hope it would be fixed someday. Before it was still tracking the pages (I could see the tables fill up) but the piwik interface didn't display anything of data. After DST went in effect, visits showed up again in the interface.

The piwik data misteriously shows up after DST time changes. This is very strange. There is a bug of some sort in the archive selection code for sure!